CZ2007576A3 - Recycling process of waste polyurethane foams - Google Patents

Abstract

The present invention relates to a process for recycling waste polyurethane foam to a polyol blend in that the waste polyurethane is decomposed by reaction with a low molecular weight polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, trimethylolpropane, glycerol, or mixtures thereof, wherein the waste polyurethane and polyhydric alcohol are at least 3/1 by weight and at most 1/3, and the reaction mixture is exposed to electromagnetic radiation at a frequency of 1 MHz to 10 GHz at 50 degC to 300 degC.

Description

Technical field

The invention relates to a low-energy process for recycling waste polyurethane foams to a polyol blend applicable to the production of novel polyurethane expanded and compacted materials.

BACKGROUND OF THE INVENTION

Polyurethane foam (soft, semi-hard, hard, integral, etc.) accounts for more than 50% by weight of the total polyurethane production. The considerable production of this material is inextricably linked to the increasing amount of polyurethane waste and the need for its efficient reuse by recycling. Polyurethane foam is one of the thermosetting plastics which can be decomposed into monomers (oligomers) useful for the production of the new polyurethane by the action of a suitable chemical agent. Processes based on its hydrolysis, aminolysis, glycolysis or alcoholysis can be used to decompose polyurethanes.

Hydrolysis of polyurethanes is based on the application of superheated water vapor to hydrolyze urethane bonds to form polyols and amines (U.S. Pat. Nos. 4,025,559; US 4,339,236). After separation and purification, they can be reused as raw materials for the production of polyurethanes. However, the separation and purification of PUR hydrolysis products is so expensive that this process is not economically viable.

Aminolysis of PUR is based on the cleavage of urethane bonds by amines (eg, dibutylamine or ethanolamine) to polyols and disubstituted urea. The end products are oligomeric ureas and amines (Kanaya, K., Takahashi, S., J.Appl. Polym.Sci., 51,675, 1994).

The most suitable and currently also industrially used method of chemically decomposing a polyurethane polymer network into a polyol blend is glycolysis using high boiling glycols as decomposers (US Patents 3,983,087; US 4,044,046; US 4,159,972; US 5,300,530; US 5,357,006; US 5,410,008; US 5,556,889;

5,635,542; US 5,684,054; US 5,691,389; US 5,763,692; US 6,020,386; US

6,069,182; US 6,683,119; US 6,750,260).

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The common disadvantage of all known processes for the glycolysis of polyurethanes is the high energy demand and long reaction times, which significantly limits their industrial applicability.

It has been experimentally found that the entire glycolysis process can be greatly streamlined by using low-energy microwave radiation to heat the reaction mixture, resulting in a significant reduction in glycolysis energy costs and a shortening of reaction time. Microwaves represent non-destructive non-ionizing radiation (waves) of very low energy (10 ³ eV and 1 µmol ^-1 ), which penetrates the material and causes its very efficient internal heating, in which the heat flux is directed from the inner parts of the material out , which causes a high rate of heating of the reaction mixture throughout the volume regardless of its low thermal conductivity. US Patented Glycolysis Procedures (US Patents 3,983,087; US 4,044,046; US 4,159,972; US 5,300,530; US 5,357,006; US

5,410,008; US 5,556,889; US 5,635,542; US 5,684,054; US 5,691,389; US

5,763,692; US 6,020,386; US 6,069,182; US 6,683,119; US 6,750,260) do not mention microwave heating and include only conventional conductive heating of the reaction mixture by the action of a heat transfer medium (most commonly silicone oil or superheated steam). The heat flow is directed from the outside of the material to the inside, which, due to the poor thermal conductivity of the processed material, causes considerable energy losses and slows down the process.

SUMMARY OF THE INVENTION

Experiments have shown that the polyurethane foam itself does not absorb microwaves and therefore does not heat up. However, if glycol is used as the reagent, microwave absorption and very rapid heating of the reaction mixture of polyurethane foam with glycol, as well as faster dissolution of the polyurethane foam than in the case of conventional heating and subsequent decomposition of the polyurethane network into polyols - recyclate. Said microwave heating method allows the reaction mixture to overheat and thus carry out the reaction at a higher temperature without applying pressure, which greatly shortens the total glycolysis reaction time and allows the use of lower boiling glycols. Another advantage is the possibility of using a smaller excess of glycol to decompose the polyurethane foam. The recycled product consists of a mixture of several types of polyols (compounds with terminal hydroxyl groups), the dominant component of which is the original aliphatic polyol used for the production of polyurethane foam, as well as the carbamate. * · · 1 1 1 1 1 1 1 1 1 1 1 1 1.... Polyol - a derivative of the original isocyanate, most often polymeric bis (4-isocyanatophenyl) methane (PMDI) or a mixture of 2,4- and 2,6-diisocyanatotoluene (TDI) and unreacted glycol, which is dosed in excess in the reaction mixture. Furthermore, it has been found that the recycled material thus obtained can be used alone or in admixture with virgin polyols as a polyol component in the preparation of a new polyurethane, lightweight or compact, without adversely affecting the performance properties of the PUR product.

Based on this knowledge, a low-energy method of recycling waste polyurethane foams has been proposed, which advantageously uses microwave radiation to heat and decompose the polyurethane network to obtain recycled (polyols) usable in the production of new polyurethane products - lightweight materials (soft, semi-hard and hard foams) resins, paints and adhesives.

The essence of the method of recycling waste polyurethane foams to the polyol blend of the present invention is that waste polyurethane is decomposed by reaction with a low molecular weight polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, diethylene , triethylene glycol, tripropylene glycol, trimethylolpropane, glycerol, or mixtures thereof, with the waste polyurethane and polyhydric alcohol being at a weight ratio of at least 3/1 and at most 1/3 and the reaction mixture heated by the effect of electromagnetic radiation at a frequency in the 1MHz to 10 range GHz to 50 ° C to 300 ° C.

The process for recycling waste polyurethane foams to a polyol mixture may preferably be carried out by catalyzing the glycoytic reaction by adding monoethanolamine or diethanolamine, or triethanolamine, or sodium hydroxide, or potassium hydroxide, or sodium etholate, or potassium etholate, or titanium butoxide, or titanium isopropoxide, or titanium npropoxide, or mixtures thereof in any ratio, the catalyst in a weight ratio to the polyurethane foam of 1/500 to 1/10.

This microwave glycolysis technology of waste polyurethane foams according to the invention is very energy efficient as it saves up to 70% of electrical energy compared to previously established glycolysis processes and provides valuable resulting products that can be further directly used for polycondensation of polyurethanes or subjected to further easy processing.

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DETAILED DESCRIPTION OF THE INVENTION

Example 1

Crushed soft polyurethane foam based on polymeric 4,4'-diphenylmethane diisocyanate (MDI) and polyether polyol of 55 kg / m ³ in an amount of 100 g was mixed with dipropylene glycol in a weight ratio of 1: 1.5 and subsequently heated in the reaction vessel by microwave radiation with a power input of 1 kW and a frequency of 2.45 GHz for 10 minutes. During this time, the polyurethane was completely glycolyzed to a mixture of polyols having a density of 1070 kg / m ³ , a hydroxyl value of 476 mg KOH / g, an acid number of less than 0.1 mg.KOH / g, a water content of 0.8% by weight. The viscosity of the product at 23 ° C was 1850 mPa.s.

For comparison, glycolysis of the same polyurethane foam was performed using conventional heating: The pulp of the same polyurethane foam based on polymeric MDI and polyether polyol of 55 kg / m ³ in an amount of 100 g was mixed with diethylene glycol in a 1: 1 weight ratio. The ratio of kPUR foam 1/100 and then in the reaction vessel was heated in an electric heating nest at 210 ° C for 2.5 h. During this time the polyurtane was completely glycolyzed to a mixture of polyols with a density of 1060 kg / m ³ , viscosity 2069 mPa. (23 ° C), a hydroxyl value of 372 mg KOH / g, an acid number of less than 0.1 mg, KOH / g and a water content of 0.8 wt.

The experimental conditions and product analysis results are summarized in the Table

1. Comparison shows that microwave heating of the reaction mixture leads to faster polyurethane decomposition and lower energy consumption.

Example 2

Crushed soft polyurethane foam based on polymeric 4,4'-diphenylmethane diisocyanate (MDI) and polyether polyol of 55 kg / m ³ in an amount of 100 g was mixed with diethylene glycol in a weight ratio of 3: 1 and catalyst diethanolamine in a weight ratio of 1/500 and then heated in the reaction vessel by microwave radiation with a power input of 1 kW and a frequency of 2.45 GHz for 15 minutes. During this time, PUR was completely glycolyzed to a biphasic liquid polyol mixture. The upper / lower phase weight ratio of the product was 3/4. The density of the upper phase of the product was 1030 kg / m ³ , the viscosity at 23 ° C was 6500 mPa.s, the hydroxyl value was 181 mg KOH / g, the acid number was less than 0.1 mg.KOH / g and the water content 0.8% wt. . The lower product density of 1090 kg / m ³ had a viscosity of 550 mPa.s at 23 ° C, a hydroxyl value of 680 mg KOH / g, an acid number of less than 0.1 mg KOH / g and a water content of 0.9% by weight.

For comparison, glycolysis of the same polyurethane foam was performed using conventional heating: The pulverized soft polyurethane foam based on polymeric MDI and polyether polyol of 55 kg / m ³ in an amount of 100 g was mixed with diethylene glycol in a 1: 1 ratio by weight. weight ratio to 1/100 polyurethane foam and subsequently heated in an electric heating nest at 210 ° C for 2.5 h. During this time, the polyurethane was completely glycolyzed to a biphasic liquid mixture of polyols. The weight ratio of the upper / lower phase of the product was 2/3. The density of the upper product phase was 1.03 kg / m ³ , the viscosity at 23 ° C was 1842 mPa.s, the hydroxyl value was 218 mg KOH / g, the acid number was less than 0.1 mg.KOH / g and the water content 0.8 % wt. The lower phase of the product, having a density of 1.09 kg / m ³ , had a viscosity of 337 mPa.s at 23 ° C, a hydroxyl value of 542 mg KOH / g, an acid number of less than 0.1 mg KOH / g and a water content of 0.9% hm.

Experimental conditions and product analysis results are summarized in Table 1. The comparison shows that microwave heating of the reaction mixture results in faster polyurethane decomposition and lower energy consumption.

Example 3

Crushed soft polyurethane foam based on polymeric 4,4'-diphenylmethane diisocyanate (MDI) and polyether polyol of 55 kg / m ³ in an amount of 100 g was mixed with ethylene glycol in a ratio of 1: 3 and potassium hydroxide catalyst in a ratio of kPUR foam 1 / 100 and then heated in the reaction vessel by microwave radiation with a power input of 1 kW and a frequency of 915 MHz for 8 minutes. During this time, PUR was completely glycolyzed to a biphasic liquid polyol mixture. The weight ratio of the upper / lower phase of the product was 1/3. The density of the upper product phase was 1030 kg / m ³ , the viscosity at 23 ° C was 2570 mPa.s, the hydroxyl value was 211 mg KOH / g, the acid number was less than 0.1 mg.KOH / g and the water content 0.6% wt. . The lower product density, 1090 kg / m ³ , had a viscosity of 52 mPa.s at 23 ° C, a hydroxyl value of 1558 mg KOH / g, an acid number of less than 0.1 mg KOH / g and a water content of 0.9% by weight.

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For comparison, glycolysis of the same polyurethane foam was performed using conventional heating: The pulverized soft polyurethane foam based on polymeric MDI and polyether polyol of 55 kg / m ³ in an amount of 100 g was mixed with ethylene glycol in a 1: 1 weight ratio a 1/100 kPUR foam ratio and subsequently heated in an electric heating nest at 190 ° C for 3.5 h. During this time, the PUR was only partially glycolyzed to a biphasic liquid polyol mixture, the content of unglycolyzed solids being 6%. % wt. The weight ratio of the upper / lower phase of the product was 1/5. The density of the top phase of the product was 1.05 kg / m ^3, viscosity at 23 ^at c was 2354 mPa.s, hydroxyl number 818 mg KOH / g, an acid number less than 0.1 mg.KOH / g and water content 0.8 % wt. The lower product phase having a density of 1.09 kg / m ³ , had a viscosity of 878 mPa.s at 23 ° C, a hydroxyl value of 1285 mg KOH / g, an acid number of less than 0.1 mg KOH / g and a water content of 0.8% hm.

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The experimental conditions and product analysis results are summarized in Table 1.

The comparison shows that microwave heating of the reaction mixture leads to faster decomposition

PUR and lower energy consumption.

Table 1: Comparison of experimental conditions and product analysis results

Example 1 Example 2 Example 3 Heating method MW conduction MW ’ conduction MW conduction Reagent Dipropylene glycol Dipropylene glycol Diethylene glycol Diethylene glycol Ethylene glycol Ethylene glycol Reaction time 10 min 2,5 h 15 min 2,5 h 8 min 3,5 h Weight, ratio PUR foam / glycol 1 / 1.5 1/1 3/1 1/1 1/3 1/1 Unreacted foam content, wt. 0 0 0 0 0 6 Product viscosity at 23 ’C, mPa.s 1850 2069 6500 * 550 ** 1842 * 337 ** 2570 * 52 ** 2354 * 878 ** Hydroxyl product number, mg KOH / g 476 372 181 * 680 ** 218 * ₅ 42 ' 21Γ 1558 ** 818 * 1285 ** Acid number of the product, mg KOH / g <0.1 <0.1 <0,1 * <0,1 ** <0,1 * <0,1 ** <0,1 * <0,1 ** <0,1 * <o, r * Water content of the product,% wt. 0.8 0.8 0.8 0.9 0,8 * 0.9 ** 0,6 * 0.9 ** 0,8 * 0.8 **

* upper product phase ** lower product phase

Industrial applicability

The recycling method of waste polyurethane foams can be used to produce polyols for processing into polyurethane foams and paints.

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Claims (2)

PATENT CLAIMS CLAIMS 1. A method for recycling waste polyurethane foams to a polyol mixture wherein the waste polyurethane is mixed with a low molecular weight polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 2-methyl-1,3-propanediol, diethylene glycol, dipropylene glycol. , triethylene glycol, tripropylene glycol, trimethylolpropane, glycerol, or mixtures thereof, wherein the waste polyurethane and polyhydric alcohol are in a weight ratio of at least 3/1 and at most 1/3 and the reaction mixture is exposed to electromagnetic radiation at a frequency in the 1 MHz to 10 GHz range at 50 ° C to 300 ° C. A process for recycling waste polyurethane foams to a polyol mixture according to claim 1, wherein the ongoing glycolytic reaction is catalyzed by the addition of monoethanolamine or diethanolamine; or diethanolamine, or sodium hydroxide, or potassium hydroxide, or sodium ethoxide, or potassium ethoxide, or titanium butoxide, or titanium isopropoxide, or titanium n-propoxide, or mixtures thereof, in any ratio, the catalyst being in weight ratio to polyurethane 1 / 500 to 1/10.